In the last few days I've noticed that (even with the lever adjusted to its maximum 'out' distance) I have to squeeze the lever more before any decent braking occurs.
I used to cover the brake with two fingers and could squeeze enough to get some goods braking that way, now the lever comes back and pins my other fingers first.
Unsurprisingly, I don't like it.
The master was rebuilt (sleeved I believe) by the dealer workshop not too long ago when I had a little 'complete brake failure issue'. Might have been last year.
Any ideas where I could start with the diagnosis ?
If you haven't already, try bleeding it at the master cylinder banjo, messy but usually very fruitful
Check the fluid level, then brake pad thickness. If both are ok, replace fluid and bleed the system. If level is low then fill up, bleed, and squeeze the lever and keep it under tension with a cable tie for a few hours. Then remove cable tie, take calipers off and check for leaks.
Quote from: steve porter on Friday, 22 November 2019, 11:57 AM
If you haven't already, try bleeding it at the master cylinder banjo, messy but usually very fruitful
Really? never done that (or heard of that) before.
Quote from: Andre on Friday, 22 November 2019, 01:25 PM
Check the fluid level, then brake pad thickness. If both are ok, replace fluid and bleed the system. If level is low then fill up, bleed, and squeeze the lever and keep it under tension with a cable tie for a few hours. Then remove cable tie, take calipers off and check for leaks.
I doubt its the pad thickness or it wouldn't have been fine one week and poor the next - it'd be more of a linear drop off, presumably.
I hate bleeding brakes etc. Hate it. :D
Quote from: VladTepes on Friday, 22 November 2019, 01:34 PM
I doubt its the pad thickness or it wouldn't have been fine one week and poor the next - it'd be more of a linear drop off, presumably.
Agree.
Take the calipers off and the pads out and check that all the pistons move smoothly. Over time you get a build up of brake dust between the two smaller (outer) pistons and the outside edge of the caliper which either gums up the piston and stops it working or slows it down. If this happens just on one side then it means only one pad is effectively doing the work..
Clean the whole piston area with a toothbrush and some brake cleaning fluid, check pistons run smoothly (they also can get a hard ring of dust on them that needs cleaning off) and try your bakes again.
Also check that the bobbins on the disc turn easily, one other "cause" could be the disc isn't floating.
Lastly, if none of the above work, check run out on your discs, it's possible one has warped.
Quote from: VladTepes on Friday, 22 November 2019, 01:34 PM
Quote from: steve porter on Friday, 22 November 2019, 11:57 AM
If you haven't already, try bleeding it at the master cylinder banjo, messy but usually very fruitful
Really? never done that (or heard of that) before.
Yep really, my radial Brembo M/C even has a bleed nipple, sometimes it's the only way or can at least save you hours of bleeding fun
Quote from: Andre on Friday, 22 November 2019, 01:25 PM
Check the fluid level, then brake pad thickness. If both are ok, replace fluid and bleed the system. If level is low then fill up, bleed, and squeeze the lever and keep it under tension with a cable tie for a few hours. Then remove cable tie, take calipers off and check for leaks.
I doubt its the pad thickness or it wouldn't have been fine one week and poor the next - it'd be more of a linear drop off, presumably.
I hate bleeding brakes etc. Hate it. :D
Sounds like the master cylinder to me.
Vlad, do you have a pair of brake hose clamps. They will diagnose for you. Clamp off line from master, if no better then thats problem, either air in banjo or cylinder no good. Bleed banjo and re try. If still no better, master cylinder stuffed. If better with line clamped, then clamp off each side to calipers, just see which side gets harder feel. Softer side is the problem.
Quote from: gsxbarmy on Friday, 22 November 2019, 04:33 PM
Take the calipers off and the pads out and check that all the pistons move smoothly. Over time you get a build up of brake dust between the two smaller (outer) pistons and the outside edge of the caliper which either gums up the piston and stops it working or slows it down. If this happens just on one side then it means only one pad is effectively doing the work..
Clean the whole piston area with a toothbrush and some brake cleaning fluid, check pistons run smoothly (they also can get a hard ring of dust on them that needs cleaning off) and try your bakes again.
Also check that the bobbins on the disc turn easily, one other "cause" could be the disc isn't floating.
Lastly, if none of the above work, check run out on your discs, it's possible one has warped.
That ^^
It's ALWAYS sticky pistons when my lever travel increases. It's how I decide it's time to clean the calipers again tbh.
Note Bleed nipple on Radial M/C, although messier, as long as you have water handy bleeding from the banjo is pretty effective. I put braided lines on at least a dozen early 90`s Ducatis , and the only way to get a good lever was to bleed at the banjo after having the lever pulled in overnight with a cable tie.
(https://i.imgur.com/GFWs992.jpg)
I've travelled 140,000km's over 18 years and never cleaned the calipers pistons :facepalm: :facepalm: should I be expecting brake fade ??????
Quote from: VladTepes on Friday, 22 November 2019, 11:04 AM
In the last few days I've noticed that (even with the lever adjusted to its maximum 'out' distance) I have to squeeze the lever more before any decent braking occurs.
I used to cover the brake with two fingers and could squeeze enough to get some goods braking that way, now the lever comes back and pins my other fingers first.
Unsurprisingly, I don't like it.
The master was rebuilt (sleeved I believe) by the dealer workshop not too long ago when I had a little 'complete brake failure issue'. Might have been last year.
Any ideas where I could start with the diagnosis ?
Maybe a silly question but are you still running the original rubber hoses? I got new braided lines on order cause i felt the same issue creeping up, i was a) amazed at how much the rubber lines actually swell during braking and b)impressed they still work after 15 years.
May be time to change the hoses if they are still OEM rubber.
Nah braided lines
Also brakes have been apart when powdercoating done and rebuilt with new rotors and pads - so should be no issues there.
Brakes are also 4 pot calipers (replaced the standard 6-pots with ones from gsxr something)
No, haven't got any brake hose clamps but I presume they wouldn't work with braided lines in any event.
None of those changes were made recently.
At one point my M/C did go - lost all front brakes (exciting) and the local suzuki dealer (team moto ::) ) sleeved it or some such. It seemed fine after that - was a while back now.
But too good to last maybe....
Dud steer from me Vlad. Clamps on braided no go.
Checked master cylinder reservoir and its full.
Not sure how I'd go about bleeding from the banjo?
Sure it would hget pretty bloody messy.
Whether I do that or not though, I'll still need to bleed the lines to make sure no air in there, does it matter whether to do LHS or RHS caliper first?
Generally you do the furthest from the master first, if you've got dual lines off the master, then I'd suggest it doesn't matter which one you start with.
I used some Bendix ultra premium stuff, it's blue (got it from SCA) you'll be able to tell when you're onto the new fluid if you use something like that.
Quote from: VladTepes on Wednesday, 27 November 2019, 12:46 PM
Checked master cylinder reservoir and its full.
Not sure how I'd go about bleeding from the banjo?
Sure it would hget pretty bloody messy.
Whether I do that or not though, I'll still need to bleed the lines to make sure no air in there, does it matter whether to do LHS or RHS caliper first?
[/quote
Just put a rag under it and put pressure on the lever and crack the banjo nut pulling in the lever, tighten nut and repeat a few times.Rinse with water and job done, may not be that, but it certainly won`t hurt to check that no air is trapped in there, I always do it as a matter of course these days.